1. Field of the Invention
This invention relates generally to a manually actuated electrical switching device for preventing inadvertent activation of electrically powered circuitry, and, particularly, to a manually actuated on/off power switch, for an emergency position indicating radio beacon (EPIRB) or personal locating beacon (PLB), that prevents inadvertent manual activation of the power switch, and thus inadvertent activation of the device and transmission of RF energy signals, thereby preventing the unnecessary deployment of search and rescue forces.
2. Description of Background Art
An emergency position indicating radio beacon, and similarly a personal locator beacon, transmits emergency geographical latitude and longitude positional information by radiating an RF signal at a predesignated specific RF frequency, or frequencies, allotted only for use in emergency situations in order to aid search and rescue and/or police and military activities in locating the person in possession of the radio beacon.
EPIRBs are commonly deployed on marine vessels for manual activation in an emergency situation. The EPIRBs are commonly stored in an easily accessible location for quick deployment in the event that an emergency situation arises. Once activated, the EPIRB transmits signals that can either provide direction finding information, such as radar direction information, to search and rescue vehicles, or transmits identification beacon signals that may be received by Search and Rescue Satellite Aided Tracking (SARSAT) satellites in orbit around the earth.
SARSAT uses the identification beacon signal received from an EPIRB to determine approximate position coordinates of the EPIRB, and transmits the approximate geographic latitude and longitudinal positional coordinates of the transmitting EPIRB, along with other pre-programmed information received from the EPIRB, such as the name of the vessel, to ground stations. The ground stations then relay the information to a rescue coordination center which deploys rescue craft to the approximate EPIRB position to begin search and rescue operations. In addition, direction finding signals from the EPIRB may be directly received by search and rescue vessels and aircraft capable of receiving such transmissions to help locate the transmitting EPIRB.
Operation of an EPIRB as described above, is fully disclosed in U.S. Pat. No. 5,218,366, issued to Cardamone et al. Since EPIRB's are battery powered, the power switch typically has a test position to check the battery charge to make sure that the device is fully capable of transmitting an emergency signal, even though a signal is not transmitted when the switch is in the test position.
Another type of outdoor emergency geographical position locating device is a personal locator beacon (PLB). This device includes a radio transmitter that transmits an RF frequency signal at predetermined emergency frequencies, similar to an EPIRB, and can be used outdoors by campers, hikers, skiers, mountain climbers, boaters, or anyone that may find themselves lost, or in a survival situation, and in need of emergency assistance. Again, the PLB has a manually actuated power switch for activation and the switch typically includes a test position for testing battery capacity without actually transmitting a signal.
EPIRB's and PLB's are typically fabricated with a watertight, rigid plastic housing since they are most often used in outdoor or marine environments. Accordingly, the power switch used to operate the EPIRB or the PLB must therefore be disposed within a waterproof environment. These devices also include an antenna that is connected to the electrical circuitry inside for radiating energy outwardly.
Accordingly there exists a need for a water-proof, manually actuated power switch having positions for power on, power off, and battery test, that is not subject to inadvertent actuation, for use with emergency rescue transmitting devices and the like.